Method for producing coated metal surfaces and the use of said metal surfaces

ABSTRACT

The invention relates to a method for producing coated metal surfaces at a coating speed of at least 25 m per minute during the application of a pre-treating agent to a cleaned and/or pickled metal surface. The inventive method is characterized by applying at least one pre-treating agent to at least one surface of a metal body after cleaning and/or pickling the metal surface to be treated. At least one lacquer layer is applied to a part of the pre-treated surface, the coating produced only by the pre-treating agent and not by the lacquer being used as the treatment layer instead of a priming or pre-treatment layer. The invention further relates to a method for producing coated metal surfaces at a coating speed of at least 25 m per minute during the application of a pre-treating agent to a cleaned and/or pickled metal surface. The inventive method is characterized by applying at least one pre-treating agent to at least one surface of a metal body after cleaning and/or pickling the metal surface to be treated. At least one lacquer layer is applied to at least a part of the pre-treated surface, the coating produced only by the pre-treating agent being used as the treatment layer instead of a priming or pre-treatment layer.

[0001] The present invention relates to a method for producing coated metal surfaces in which the coating can be carried out at high speed. Such coatings are often used under the description “coil coating” to coat strip materials.

[0002] The known high-speed coating methods have the disadvantage that the pretreatment and the priming (primer) are applied in two separate steps.

[0003] The object of the invention is to provide a process for the large-scale industrial production of lacquered strip materials in which the pretreatment and priming can be applied in only one work stage.

[0004] This object is achieved by a process for producing coated metal surfaces at a coating speed of at least 25 m per minute in the application of a pretreatment agent to a cleaned and/or pickled metal surface, which is characterised in that at least one pretreatment agent, in particular a solution and/or dispersion, is applied to at least one surface of a metal body after a cleaning and/or a pickling of the metal surface to be treated and at least one lacquer layer is then applied to a part of the pretreated surface, with the coating produced only using a pretreatment agent and not using a lacquer being used, instead of a pretreatment layer and a priming layer, as treatment layer.

[0005] Furthermore the object is achieved by a process for producing coated metal surfaces at a coating speed of at least 25 m per minute in the application of a pretreatment agent to a cleaned and/or pickled metal surface, which is characterised in that at least one pretreatment agent, in particular a solution and/or dispersion, is applied to at least one surface of a metal body after a cleaning and/or a pickling of the metal surface to be treated and at least one lacquer layer is then applied to a part of the pretreated surface, with the coating treated with a pretreatment agent being used, instead of a pretreatment layer and a priming layer, as treatment layer.

[0006] Preferably the pretreated surface or surfaces form one side of a strip, in which optionally at least one of the narrow edge surfaces of the strip may also be partially pretreated.

[0007] The coating speed is preferably 40 to 600 m per minute, particularly preferably 75 to 160 m per minute. The treatment layer thereby assumes the functions of the primer. The other part of the pretreated surface is subsequently no longer coated with a lacquer in the strip coating device.

[0008] The method according to the invention may be employed so that moisture or residual moisture is retained in the applied pretreatment layer until lacquering is performed, in order to adjust the necessary electrical conductivity of the pretreated surface for the application of the lacquer layer.

[0009] The metal surface may before the pretreatment contain in particular aluminium, iron, copper, magnesium, zinc and/or tin and may preferably consist of an aluminium alloy, a hot-dip galvanised or electrolytically galvanised iron material, a steel, a full zinc material in the form of strips or metal sheets, or tinplate. In this connection the bodies may be flat or shaped, or may be provided with recesses, such as for example with a perforated structure.

[0010] The recesses of a perforated plate may all have the same geometry and size, or may optionally also have different geometries and sizes, for example circular holes, elongate holes or slits.

[0011] The cleaning and/or the pickling of the metal surfaces may be carried out by spraying and/or brushing with a cleaning and/or pickling solution or immersion in a bath of this solution.

[0012] The pretreatment of the cleaned and/or pickled surface may be performed by spraying and squeezing out, for example with a roller, by spraying and blowing off, for example with compressed air, by immersion and squeezing out, for example with a roller, by immersion and blowing off, for example with compressed air or in a roll-coat process. With the roll-coat process the treatment liquid is applied with a coating roller in or against the direction of movement of the strip. In all these process variants, no subsequent rinsing is performed in order to prevent removing and/or damaging the applied layer and to avoid rinse water loaded with chemicals, which for environmental reasons, would have to be post-treated in a complex procedure.

[0013] The pretreatment agent may be a preparation containing a polymer dispersion with at least one resin from the group consisting of acrylate, epoxide, phenol, polyester, silicone polyester, polyurethane, styrene and urea-formaldehyde based resin or a mixture thereof and/or a mixed polymer. The preparation contains, apart from volatile constituents, a non-volatile film-forming mixture. The preparation may contain at least one resin as solution and/or as dispersion. The preparation may contain, apart from resin(s), at least one inorganic additive in dissolved form and/or as a finely divided powder, for example a carbonate, chromate, oxide, phosphate, silicate or sulfate.

[0014] The pretreatment agent may also be a resin-free preparation, with it being possible for the preparation to contain aluminium, fluoride, hydrofluoric acid, phosphate, phosphoric acid, trivalent and/or hexavalent chromate, chromic acid, silicate, silane, tannin, titanium, zinc, zirconium and/or self-organising molecules, for example based on phosphonates, carboxylic acids, thiols and/or silanes.

[0015] For the application to a metal strip a different pretreatment agent may be chosen for one side of the strip than for the other side, with it being possible for the side not intended to be subsequently lacquered to be coated with a pretreatment agent containing organic resin. For example only one side of the strip, say the upper side, is possibly lacquered, whereas, on the opposite side, the pretreatment acts as a final treatment.

[0016] After the application of the treatment agent the layer may either be partially dried or completely dried. This may be carried out—especially with uniform strip speeds and when using existing ovens—by a shorter residence time under the active drying conditions, by a lower temperature in the oven, and/or by a reduced air movement for the drying of the strip.

[0017] Preferably at least one side of the pretreated surface is coated with an organic coating that hardens sufficiently and/or crosslinks in a time from 1 second up to 3 minutes, particularly preferably from 5 seconds up to 2 minutes.

[0018] For the coating of the pretreated surface, a powder lacquer, in particular a powder lacquer having good mechanical properties, high scratch resistance, good adhesion and high flexibility as regards forming and shaping, is preferably applied and stoved. The powder lacquer may in this connection be applied by spraying, fluidised-bed powder sintering and/or powder cloud technology and stoved. Powder cloud technology is described in, inter alia, EP-A-0 678 466. Instead of by conventional circulating air drying or fluidised air drying, the stoving may be carried out by, in particular by conductive drying using magnetic materials, and/or by infra-red drying, in particular in the near infra-red (NIR).

[0019] The pretreatment layer and/or treatment layer may, after complete drying, have a layer thickness in the range from 0.1 to 50 μm, preferably in the range from 0.5 to 10 μm, particularly preferably in the range from 1 to 3 μm.

[0020] After the crosslinking, the stoved lacquer layer that is contained on the pre-treatment layer may have a layer thickness in the range from 5 to 1000 μm, preferably in the range from 10 to 400 μm, and particularly preferably in the range from 15 to 60 μm. When using PVC plastisols it is possible to recommend selection of a layer thickness in the range from 100 to 300 μm.

[0021] In a preferred embodiment of the method according to the invention a one-layer cover lacquer is applied as a single lacquer to the strip to be coated.

[0022] A treatment layer that performs the function of a pretreatment and at the same time that of a primer can be formed with the pre-treatment agent. The primer in this connection performs the function of corrosion prevention, satisfies the adhesion and flexibility requirements, and to a minor extent also performs an aesthetic function.

[0023] There may be used for the powder lacquer a powder for a single-colour unstructured coating, a powder for a multicolour unstructured coating, and/or a powder for a multicolour structured coating.

[0024] The coated surface may be protected, in particular against mechanical damage, for example during storage, transportation and further processing, at least partially by a film or adhesive film.

[0025] The coated bodies may optionally be shaped, cut—especially in the longitudinal and/or transverse direction—and optionally re-formed, for example beaded, roll-formed, deep-drawn and/or edged.

[0026] The products formed by the method according to the invention may be used as internal and external panelling, equipment panelling, e.g. for domestic appliances and small electrical instruments, in particular with decorated external panelling, perforated metal sheets, especially for loudspeakers and sound insulating cladding, space dividers, partitions, furniture units, shelving, internal panelling for vehicles and aircraft, such as for example dashboards/instrument panels, frame and frame constructions, facing materials and lighting installations. 

1. Method for producing coated metal surfaces at a coating speed of at least 25 m per minute in the application of at least one pretreatment agent to a cleaned and/or pickled metal surface of a metal strip, characterised in that at least one pretreatment agent is applied to at least one side of the strip after a cleaning and/or a pickling of the metal surface to be treated and at least one lacquer layer is then applied to at least a part of the pretreated surface, in particular on one side of the strip, the coating produced with a pretreatment agent and not with a lacquer is used, instead of a priming and pretreatment layer, as treatment layer, with the side of the strip not intended to be subsequently lacquered being preferably coated with a pretreatment agent containing an organic resin, the side of the strip intended to be subsequently lacquered being coated with at least one pretreatment agent, preferably with a pretreatment agent that is different to that used for the side of the strip not intended to be subsequently lacquered, and the at least one lacquer layer being applied as powder lacquer to the pretreated side of the strip intended to be subsequently lacquered, and is stoved.
 2. Method according to claim 1, characterised in that the moisture or residual moisture in the applied pretreatment layer is retained until the lacquering in order to adjust the necessary electrical conductivity of the pretreated surface for the application of the lacquer layer.
 3. Method according to claim 1 or 2, characterised in that the metal surface contains before the pretreatment aluminium, iron, copper, magnesium, zinc and/or tin and preferably consists of an aluminium alloy, a hot-dip galvanised or electrolytically galvanised iron material, a steel, or a full zinc material in the form of strips.
 4. Method according to one of the preceding claims, characterised in that the cleaning and/or the pickling is carried out by spraying and/or brushing with a cleaning and/or pickling solution or immersion in a bath of this solution.
 5. Method according to one of the preceding claims, characterised in that the pretreatment agent is applied by spraying and squeezing out with a roller or by immersion and squeezing out with a roller or by a roll-coat process.
 6. Method according to one of the preceding claims, characterised in that the pretreatment agent is a preparation that contains a polymer dispersion with at least one resin from the group consisting of acrylate, epoxide, phenol, polyester, silicone polyester, polyurethane, styrene and urea-formaldehyde based resin or a mixture thereof and/or a mixed polymer.
 7. Method according to one of the preceding claims, characterised in that the pretreatment agent is a preparation that contains at least one resin in the form of a solution and/or dispersion.
 8. Method according to one of the preceding claims, characterised in that the pretreatment agent is a preparation that contains, apart from resin(s), at least one inorganic additive in dissolved form and/or as finely divided powder, for example a carbonate, chromate, oxide, phosphate, silicate or sulfate.
 9. Method according to one of the preceding claims, characterised in that the pretreatment agent is a resin-free preparation that contains aluminium, fluoride, hydrofluoric acid, phosphate, phosphoric acid, trivalent and/or hexavalent chromate, chromic acid, silicate, self-organising molecules, silane, tannin, titanium, zinc and/or zirconium.
 10. Method according to one of the preceding claims, characterised in that, for the application to a strip a pretreatment agent is selected for one side of the strip that is different to that selected for the other side, with it being possible for the side that is not intended to be subsequently lacquered to be coated with a pretreatment agent containing organic resin.
 11. Method according to claim 5, characterised in that the layer applied with the pretreatment agent is either partially dried or completely dried.
 12. Method according to one of the preceding claims, characterised in that at least one side of the pretreated surface is coated with an organic coating that hardens and/or crosslinks sufficiently in a time of 1 second up to 3 minutes, preferably in a time of 5 seconds up to 2 minutes.
 13. Method according to claim 12, characterised in that, for the coating of the pretreated surface, a powder lacquer having good mechanical properties, high scratch resistance, good adhesion and high flexibility with regard to forming and shaping is applied and stoved.
 14. Method according to one of the preceding claims, characterised in that the powder lacquer is applied by spraying, fluidised-bed powder sintering and/or powder cloud technology and stoved.
 15. Method according to one of the preceding claims, characterised in that, after complete drying, the pretreatment layer and/or treatment layer has a layer thickness in the range from 0.1 to 50 μm, preferably in the range from 0.5 to 10 μm, particularly preferably in the range from 1 to 3 μm.
 16. Method according to one of the preceding claims, characterised in that the stoved lacquer layer after the crosslinking has a layer thickness in the range from 5 to 1000 μm, preferably in the range from 10 to 400 μm, particularly preferably in the range from 15 to 60 μm.
 17. Method according to one of the preceding claims, characterised in that a single-layer cover lacquer is applied as sole lacquer at high speed.
 18. Method according to one of the preceding claims, characterised in that a treatment layer that performs the function of a pretreatment and primer is formed with the pre-treatment agent.
 19. Method according to one of the preceding claims, characterised in that a powder for a single-colour unstructured coating, a powder for a multicolour unstructured coating, and/or a powder for a multicolour structured coating is used.
 20. Method according to one of the preceding claims, characterised in that the coated surface is protected at least partially by a film or adhesive film.
 21. Method according to one of the preceding claims, characterised in that the coated bodies are optionally shaped or formed, cut—especially in the longitudinal and/or transverse direction—and optionally reformed, for example beaded, roll-formed, deep-drawn and/or edged.
 22. Use of the products produced by the method according to claims 1 to 21 as internal and external panelling, equipment panelling, e.g. for domestic appliances and small electrical instruments, in particular with decorated external panelling, perforated metal sheets, especially for loudspeakers and sound insulating cladding, space dividers, partitions, furniture units, shelving, internal panelling for vehicles and aircraft, such as for example dashboards/instrument panels, frame and frame constructions, facing materials and lighting installations. 